Method for removing cutting and grinding burrs from machined injection needle tubes

ABSTRACT

A method is provided for removing the cutting and grinding burrs sticking to or generated at the cut or ground tips of injection needle tubes. A high pressure water stream is sprayed over injection needle tubes cut to a specified length or ground at one end. The needle tubes are held upright closely adjacent to one another within a water-draining basket stretched at the bottom with a metal wire-net or the like, and the basket is put on a metal wire net conveyor continuously moving at a slow rate.

United States Patent 1 1 Wada [54] METHOD FOR REMOVING CUTTING ANDGRINDINGBURRS FROM MACHINED INJECTION NEEDLE TUBES [76] Inventor: ShojiWada, 4-11, Katase-Kaigan, 1-

chome, Fujisawa-shi, Kanagawaken, Japan [22] Filed: Dec. 22, 1970 [21]Appl. No.: 100,717

[52] US. Cl ..5l/28l R, 29/421, 29/427, 51/320 [51] Int. Cl ..B24c 1/00[58] Field of Search ....51/281 R, 323, 285, 317-321, 51/227 H; 29/558,421, 427, 81, 90, 89.5; 83/701,177; 18/5 BS; 72/56 [56] References CitedUNITED STATES PATENTS 2,138,520 11/1938 Elliot ..5l/285 X M lMarch 13,1973 3,524,367 8/1970 Franz ..s3/177x 3,543,619 12 1970 Hellmer ..s3177x 2,761,250 9/1956 Molinari ..51 2271-1 Primary ExaminerDonald G.Kelly Attorney-James E. Armstrong and Ronald S. Cornell [57] ABSTRACT Amethod is provided for removing the cutting and grinding burrs stickingto or generated at the cut or ground tips of injection needle tubes. Ahigh pressure water stream is sprayed over injection needle tubes cut toa specified length or ground at one end. The needle tubes are heldupright closely adjacent to one another within a water-draining basketstretched at the bottom with a metal wire-net or the like, and thebasket is put on a metal wire net conveyor continuously moving at a slowrate.

3 Claims, 9 Drawing Figures PATENTEUMAR I aim SHEET 2 [IF 2 a; M N a m:

METHOD FOR REMOVING CUTTING AND GRINDING BURRS FROM MACHINED INJECTIONNEEDLE TUBES BACKGROUND OF THE INVENTION In general an injection needleshould be manufactured with high dimensional accuracy. From a standpointof safety and hygiene in use, the needle surface must be well polished;the inside wall of the needle must have the least possible flowresistance, and must be beautiful and sanitary; and, moreover, theneedle itself must meet specified high standards of toughness andrigidity. For these reasons, injection needles are machined from finetubes of 18-8 stainless steel with a rich content of nickel.

To produce injection needles of fine stainless steel tubes by grindingone end of the tubes, the following method is used: A large number ofstainless steel tubes cut to a specified length are arranged in rowswith one end of each tube being clamped between two holding plates,upper and lower, of a jig. The other ends of the aligned tubesprojecting over the jig are ground by a grinder to form a main bevel ata specified angle. Next, one of the holding plates of the jig is shiftedright or left so as to turn the tubes to a different angle and then bothsides of the main bevel. are ground to form side bevels, therebyproducing injection needle tubes with a piercing point at the tip.

In the above process of cutting the stainless steel tubes or grindingthem to form the main and side bevels, burrs develop and stick, coveringthe cut or ground portions of the tubes even if wet grinding isperformed under the best of grinding conditions. Such a result isinevitable from the nature of the material of the tubes.

The complexity of the burr-removing step, the excess time needed forthis step, and the inadequacy of the removal technique have impeded theproduction of injection needles on a conveyor-line basis or on a massproduction basis and at the same time have resulted in products ofinferior quality.

Thus, the most important problem to be solved in the manufacture ofinjection needles is to work out a method and apparatus that cancompletely remove the cutting and grinding burrs without dulling theneedle point, without deteriorating the toughness and rigidity of theneedle, or without discoloring the needle point; and can make itpossible to mass-produce cheap needles in demand quantities with reducedmanpower and increased productivity.

Various methods now used for removing the needle burrs have drawbackswhich result in poor quality of products and such methods are not fitfor mass production.

In one of these methods, a skilled worker has to remove the burrs fromeach cut or ground needle tube, using a burr-removing jig. Although thequality of the needle is not deteriorated during burr removal, thismethod is time-consuming, with each tube being manually handled, andaccordingly is so inefficient that it cannot produce enough needles tomeet the demand. Besides, even a skilled worker could accidentallydamage the point and, therefore, rejects are not precluded. Moreover,the job itself being skilled labor, it takes certain length of time totrain a qualified worker and accordingly recruiting necessary workers isnot easy.

In another method, which is called chemical polishing, an acid solutioncomposed of several acids is boiled; the burred portion of the injectionneedle is immersed in this solution to remove the burrs through etching;then the needle is dipped into an alkaline solution to neutralize theacid, and finally the needle is washed with water.

When perfect removal of burrsis accomplished by this method, the needlepoint immersed in the acid solution is also etched while the burr isbeing etched and removed from the needle. Therefore, when neutralizedwith alkali and washed with water, the ground point of the needle willbe blunted, with a considerable loss in its piercing effect; moreover,the wall thickness of the needle tube is reduced and with the resultantdecrease in the toughness of the needle point, the safety of theinjection needle is lost, because the needle may bend at the tip in use.

For the simple purpose of removing the burrs, this method involves toomany steps: acid etching, alkaline neutralization, and water flushing.Furthermore each step, on account of its nature, must be performed atdifferent sites with careful attention to the work environment.

Thus, this method too is unfit for conveyor-line production; it lacksefficiency and mass-productivity. As the sharpened point of needle tubebecomes increasingly exposed to damage on account of reduction in wallthickness after each step, it is extremely difficult to handle theneedle and in consequence, rejects frequently occur in production. Itshould be noted also that chemical polishing cannot assure dimensionalaccuracy and uniformity of gloss for a large number of needles.

A third method is what is called electrolytic polishing. According tothis method, the burred portion of the needle is immersed in theelectrolyte of an electrolytic bath; the immersed needle is positive andan insoluble metal added to the electrolyte is negative; and thuselectric current develops between the two poles to dissolve and removethe burrs sticking to the needle.

If perfect removal of burrs is accomplished by this method, theelectrolyte-immersed portion of the needle also dissolves while theburrs are being dissolved and removed. The results are that the groundpoint of the needle loses its sharpness; the piercing effect of thepoint is lessened; and the toughness of the needle deteriorates with theaccompanying hazard of tip bending in use the same drawbacks recognizedwith chemical polishing. Further, electrolytic polishing comprises astep of washing with a chemical solution, so the process becomes toocomplicated for the simple purpose of burr removal. Thus the process isnot only inefficient and unsuitable for mass production, but also it hasthe same drawbacks as chemical polishing, that is, a lack of dimensionalaccuracy and uniformity of gloss in a large number of products.

A fourth method is the so-called sandblasting method. According to thismethod, sand with a desired grain size is blasted out of a nozzle,connected to the sand tank by compressed air at 4-6 atm, against the cutor ground portion of the needle, thereby removing the cutting orgrinding burrs.

In this method, the blasted portion of the needle acquires a texture ofpear skin", with the gloss being lost and the color Being changed. Atfirst glance the needle looks as if it were dirty, which may cause afeeling of uncleanliness or apprehension on the part of the user of theinjection syringe or the patient receiving the injection. Thus, the useof a blast-polished injection needle is less inviting. Besides, theground point of the needle after this method of polishing becomes dullwith a corresponding reduction in piercing effect.

In view of the productivity of this method, it could be used to processa large number of needles for burr removal at one time. For the purposeof removing the burrs from many needles at the same time with highefficiency, the bevel faces of numerous needle points must be aligned inthe same direction. Thus, blasting is done to the needle points under acovering provided over a jig which holds numerous needle tubes taken outof the grinding machine, and accordingly the precision jig is apt to bedamaged. Since the jig wears easily, the method is very costly for burrremoval. Also, the work site must be changed for each step of washing,drying, checking and so on after burr removal, and during this handlingprocess the needle point may be broken. Hence, this method is alsoinefficient, unproductive, and complicated.

A fifth method is the so-called liquid honing method. According to thismethod, a liquid blended with a finegrain abrasive is sprayed at highspeed against the cut or ground portion of the needle tube to remove thecutting or grinding burrs. This method has the same drawbacks as thesand blast method, i.e., blunting of the ground needle point,discoloration of the abrasivesprayed portion, complexity of the worksteps, high cost and lack of mass productivity.

Thus, none of the above-mentioned five conventional methods for burrremoval is free from drawbacks such as inferior product quality,excessive time required for the work, lack of mass productivity, and toohigh cost for the simple work of removing the burrs; and, accordingly,none of them is recommendable.

SUMMARY OF THE INVENTION The present invention greatly simplifies themethod for removing the burrs generated in cutting an injection needletube to a specified length and in grinding one end of the needle tubethus cut, thereby drastically reducing the time needed for burr removal.According to the invention a high quality injection needle tube with agood piercing effect in the ground state is produced by a burr-removingprocess which does not deteriorate the toughness and rigidity of theneedle tube or the needle point, and does not discolor or dull it. Thepresent invention offers a low-cost, highproductivity method forremoving the burrs, which makes it possible to put all the steps fromthe grinding of the injection needle point, the drying process and onthrough to the inspection process on a conveyor-line basis, therebyincreasing the et'ficiency ofinjection needle manufacture andeliminating the possibility of rejects in production.

According to the invention, a number of injection needle tubes cut to aspecified length or a number of thus cut injection needle tubes with oneend ground are arranged upright, in juxtaposition in a perforatedcontaining means. The container, filled with needle tubes, is carried ona slow-moving conveyor, and from above the container a pressurized waterstream is directed toward and sprayed to cover the inner and outersurfaces of all of the needle tubes passing thereunder so that thecutting and grinding burrs generated or adhered in the cutting andgrinding of the needles are removed.

BRIEF DESCRIPTION OF THE DRAWINGS The method of the present inventionwill become apparent by referring to the detailed description and theaccompanying drawings, in which: I

FIG. 1 is an elevation view of a cross-section of an injection needletube made of a fine 18-8 stainless steel tube. I

FIG. 2 is an elevation view of a cross-section of an injection needletube showing the cutting burr sticking to the cut needle portion.

FIG. 3A is an elevation view showing a ground main bevel of an injectionneedle tube; 38 is a plan view showing the grinding burr sticking to theneedle tube after the grinding of the main bevel; 3C is the elevationview corresponding to 38; 3D is a plan view showing the state of thegrinding burr sticking to the needle tube after the grinding of the sidebevel; and 3E is the elevation view corresponding to 3D.

FIG. 4 is an elevation view of the burr-removing apparatus as a whole.

FIG. 5 is an oblique view of a partial enlargement of FIG. 4.

DETAILED DESCRIPTION Usually when an injection needle tube (a) made offine stainless steel tubing is, as indicated in FIG. 1, cut to aspecified length to product injection needle 1, a large cutting burr 2develops and sticks, as shown in FIG. 2, mainly inside of the cutsection 1' of injection needle 1, covering the hole 3 of needle 1; and asmall cutting burr 2 develops and sticks outside of the cut section 1'.

When one end of needle 1 is ground to form the main bevel 4, asindicated in B, and C of FIG. 3, inside of the main bevel 4 a largegrinding burr 5, covering hole 3 of needle 1, develops and sticks, whilea small grinding burr 5' develops and sticks outside of the main bevel4. Further, when side bevels 6 are formed by grinding, as indicated inD, and E of FIG. 3, a large grinding burr 7, covering hole 3 of theneedle, develops and sticks inside of side bevels 6, while a smallgrinding burr 7' develops and sticks to ground point 8, where sidebevels 6 join.

It is strickly required that all of these burrs be completely removedfrom the injection needles in the machining stage of their manufacture,because it is practically impossible to remove them after the productsare finished. More importantly, the residual burrs will impede the flowof injected liquid during use of the needle and there is a hazard of theburr being injected into the patient's body together with the injectedliquid.

In the conventional practice of removing the burrs from an injectionneedle, one end of the needle is treated with a stainless steel brushfor burr removal or, alternately, any of the above-mentioned fivemethods for burr removal is used. The other end of the needle, which isground is also treated for removal of the grinding burrs by any ofthefive methods.

The main reasons for this practice are as follows: cutting burrs areremoved from only one cut end of the needle tube and the grinding burrsand cutting burrs are removed from the ground end after grinding. Ifboth ends are treated for removal of the cutting burrs by any of thefive methods, enormous losses in time, labor and materials will beincurred, resulting in an increased cost, an increased inefficiency andan increased deterioration of the products. As explained later, it wouldbe more convenient to remove all the cutting burrs from both cut ends ofthe needle before grinding the needle point.

The burr-removing method according to the present invention makes itpossible to remove all the cutting burrs from both out ends of theneedle tubes and all the grinding burrs can then be removed from theground Removal of Cutting Burrs A large number of injection needles 1,obtained as the result of cutting the injection needle tubes (a) made offine l8-8 stainless steel tubes, are arranged upright, close to oneanother, in heat-resistant synthetic resin basket stretched at thebottom with stainless steel wire net 9 with meshes fine enough to holdinjection needles 1, the depth of basket 10 being smaller than thelength of injection needle 1.

Meanwhile, an endless wire net belt-conveyor .12, including a drier 11positioned midway along conveyor 12 and heated by an electric heater orgas, is slowly driven by a motor. Belt-conveyor l2 carrys basket 10 fullof injection needles 1.

Above belt-conveyor 12, a pressurized water spray ejecting means, e.g.nozzle 13, connected to a high pressure pump, makes a continuousreciprocating movement in a horizontal direction across the width ofconveyor 12 and thereby directs a pressurized water spray againstneedles 1. The cutting burrs 2 and 2' sticking to one cut end of needles1 are blown off by the high water pressure.

The continuous reciprocating movement of nozzle 13 in horizontaldirection across the width of belt-conveyor l2 permits the pressurizedspray of water to cover the whole array of injection needles 1 fillingbasket 10. Thus, the traveling speed of belt-conveyor l2 and the speedof the reciprocating movement of nozzle 13 must be coordinated so as toassure full coverage of needles 1 in basket 10 by the pressurized waterspray.

As for the volume of pressurized water spray directed at the needles, atleast 50 kg/cm will be sufficient from a standpoint of efficiency, andmore than 70 kg/cm is desirable. Depending on the hardness of the needleor the quantities of burrs sticking to the needle, the preferred volumewill be about 100 kg/cm on the average.

After thus removing the cutting burrs 2 and 2' from one cut end of theneedles 1, without being passed through the drier 11, all of the needles1 are shifted to another basket 10 of the same composition, with theends now freed from the cutting burrs 2 and 2 placed downward. Theseneedles are then submitted to the same treatment as above, for removalof cutting burrs 2 and 2' from the other end thereof.

cutting burrs 2 and 2' from both ends, are subjected to the next step ofgrinding the needle point.

For the convenience of fitting the needles to the grinder jig withoutthe problem of choosing a particular end, the needles have thus beentreated on both ends for removal of all of the cutting burrs 2 and 2'.

This embodiment of the present invention has fully shown that percentremoval of cutting burrs can be expected from the use of the method andapparatus of the invention.

Removal of Grinding Burrs A large number of injection needles 1, whichhave both ends freed of cutting burrs 2 and 2' as described hereaboveand then have one end ground by a known method, are closely arrangedwith the ground end up in the same basket 10 as described above.

Next, drier 11 is heated up; belt-conveyor 12 is moved, hot water at atemperature over 40C is ejected at a rate of 100 kg/cm from highpressure water spray nozzle 13; baskets 10 are carried in succession, asshown in FIG. 4, on belt-conveyor 12; the pressure of the water sprayejected from said nozzle 13 removes the grinding burrs 5, 7 and 7 fromall of the injection needles 1; and after drying in the drier 11, thefinished injection needles 1 are obtained.

In the present case, the burr-removing apparatus is constructed andoperated in the same way as the one adopted for the removal of thecutting burrs. The results in this instance are equally satisfactorywith those described above, with practically 100 percent removal ofgrinding burrs.

In both cases, the pressurized water spray nozzle 13 is a single nozzledesigned to make a continuous reciprocating movement in a horizontaldirection across the width of belt-conveyor 12, but it may be designedas a plurality of nozzles rigidly arranged in such a way that the wholewidth of basket 10 is covered by the spray ejected from the nozzles.

As for the construction of the drier 11, any known drier may be adopted,provided that it can dry all the burr-removed needles 1 filling thebasket 10 and so long as it does not impede the travel of belt-conveyor12.

As described above, the principle in the removal of cutting or grindingburrs from injection needles according to the present invention is thesweeping of the cut or ground portion of the needle with a pressurizedwater spray. Therefore the removing process is extremely simple, safe,and very fast, the time required being about [/10 of the time requiredforthe second to fifth methods described above, and also far shorterthan the time required for the first mentioned method. Moreover, becauseno use of chemicals or abrasives and no reduction in wall thickness ofthe needle tube are involved the method of the invention is never likelyto weaken or embrittle the needle tube or the needle point, nor todiscolor them, nor to blunt the ground point. Thus the ground productexcels in dimensional accuracy and piercing effect. Because of the highgloss both outside and inside of the tube, the product is highlysanitary and safe.

In the burr-removing apparatus according to the invention, a basket fullof injection needles is carried on a belt-conveyor; the burrs areremoved while the basket is moving; and the needles with the burrsremoved are dried. Thus, once the basket is filled with many out andground needles, subsequent steps of grinding burr removal, drying andneedle point inspection can take place with the needles held in thebasket. Accordingly, the process can be put on a conveyor-line massproduction basis and this, together with the simplicity of the burrremoval step, can dramatically increase the productivity of injectionneedle manufacture. Moreover, since all the needles are held in thebasket throughout the steps of burr removal, drying and needle pointinspection and there is no need to transfer the needles to differentjigsand vessels for every step, there is no possibility of the needle pointbeing damaged and rejects being productd; thus production costs arelowered.

What is claimed is:

1. A method for removing burrs caused by cutting or grinding frominjection needles comprising a. placing a plurality of pre-cut injectionneedle tubes having burrs adhering thereto upright and in juxtapositionin a perforated container capable of retaining said tubes, and

b. contacting the inner and outer surfaces of said tubes with a waterspray under a pressure sufficient to remove the burrs from said tubes.

2. A method according to claim 1 wherein the precut injection needletubes have been previously ground on one end to form a needle point andhave grinding burrs adhering thereto.

3. A method according to claim 1 wherein the volume of water spraydirected against the surfaces of said tubes is at least 50 kg/cm.

1. A method for removing burrs caused by cutting or grinding from injection needles comprising a. placing a plurality of pre-cut injection needle tubes having burrs adhering thereto upright and in juxtaposition in a perforated container capable of retaining said tubes, and b. contacting the inner and outer surfaces of said tubes with a water spray under a pressure sufficient to remove the burrs from said tubes.
 1. A method for removing burrs caused by cutting or grinding from injection needles comprising a. placing a plurality of pre-cut injection needle tubes having burrs adhering thereto upright and in juxtaposition in a perforated container capable of retaining said tubes, and b. contacting the inner and outer surfaces of said tubes with a water spray under a pressure sufficient to remove the burrs from said tubes.
 2. A method according to claim 1 wherein the pre-cut injection needle tubes have been previously ground on one end to form a needle point and have grinding burrs adhering thereto. 